Method for removing chlorine ions from electrolytic solutions



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a air ldd ' luldhltd VIST UE ENGE LHARD'IL, 01E BERLIN-CHAELUTTENBURG, GERMANY, ASSIGNQI l TG err-n ENS HALLSKE, AKTIENGESELLSGHAFT, F SIEMENSSTADT, NEAR BERLIN, GEFJEIAIQ .iel. GillltPEllit-ATION 0E GERMAIG'Y METHOD F0 39. Il'tEI l IQ ING IGNS EERUM ELECTILWLY'IIC sonurrons Ho Drawing. Application filed lie-camber 3.5, 1926, Serial ll'o. 155,106, and in Germany December $1, 19%.

This invention relates to a new and useful method for removing chlorine ions from. electrolytic solutions, especially from. chlorinated liquid electrolytes or lyes containing zinc or other metals.

In the electrolysis oi sulphate bearing solutions, as for instance lyes containing sul phate of zinc, it is customary to use lead anodes. During the electrolytic process a superficial layer of peroxide of lead is formed on these anodes, as is well known in connection wi h storage batteries. Lead anodes are not attacked ev when stopping the electrolysis hecaus i peroxide of lead have only very lilac solubility in sulphuric acid. .ll'l the ele ,trolyte, however, contains chlorine ions a considerable corrosion of the anodes takes place during the electrolytic process. In such cases peroxide or lead and also 2Q chloride of lead are present in the hath, the

latter compound being highly soluble and producing therefore veryini urious effect on the anodes. I

The lead ions in the electrolyte disturlo the deposition of other metals, zinc etc, and

the rapid disintegration of the lead otthe anodes makes it practically impossible to carry out tie electrolysis of such solutions with success. According to publications if an M amount of chlorine ions oi aloout 200 milligrams per litre, for instance, is present in the electrolyte a corrosion of the anodes takes place'correspondi-ng to 10-l5% ot' the deposited zinc.

In the recovery of copper by electrolysis there are similar dihiculties. Therefore it is necessary to remove the chlorine as completely as possible from the solution to be electrolyzed. lt has already been proposed to add a silver salt'especially sulphate of silver, to the electrolyte, in order to eliminate the chlorine by precipitating chloride of silver without introducinp; disturbing positive ions in the solution. But this method involves the disadvantage that colloidal chloride out silver is deposited which cannot be filtred at all, or only with great difficulty. I

The present invention enables me to avoid this disadvantage. According to the inventiona'suitable body of silver, a plate for instance, is used as an anode and the electro lyt-e is forced to pass through the anode chamber which is separated from the cathode chamber by porous diaphragm. Preferably theintensity of current or the time of electrolysis is regulated in such a manner that a quantity of silver equivalent to the amount of chlorine is introduced in the solution. Since the operation is conducted. at ordinary temperature (without heating}, this quanti y of silver will at once precipitate the chlorine as flaky silver chloride which is insoluble in the electrolyte at such temperature and in this state is easily filtered. The cathode chamber is charged with electrolyte tree of chlorine. llt will be understood that the voltage employed must be suiilcient to prothrough the anode chamber in the manner set "forth and after subsequent filtering the silvercontaining lye is brought into the cathode chamber. Because oil its favourable potential of deposition the silver is quantitatively precipitated on the cathode and can be recovered.

This method afiords the advantage that the amount of chlorine in the solution to be electrolyzed need not be determined continuously for regulating the current intensity accordingly. Instead of pure silver, silver alloys may be employed for carrying this invention into effect, and I desire it to he understood that where the appended claims refer to oil ver anodes, anodes made of silver alloys are covered: as equivalents. I

What ll claim as my invention and desire to be secured by Letters Patent is:

The method of removing chlorine ions trom metal-hearing chlorinateol liqufi electrolytes, which consists in electrolyzing the liquid with a, silver anode at a voltage sufiicient to dissolve silver, for a length of time suflicient to 5 cause a quantity of silver ions at least chemically equivalent to the quantity of chlorine ions present to be dissolved in the electrolyte, at a temperature at which silver chloride is insoluble in such electrolyte, with a resulting 10 precipitation of silver chloride in a flaky condition.

In testimony whereof I aflix my signature.

VICTOR ENGELHARDT. 

